Islands of hope in the river

A wrybill checks out a new habitat. Photos: Ann-Kathrin Schlesselmann.
A wrybill checks out a new habitat. Photos: Ann-Kathrin Schlesselmann.
A black fronted tern flies over one of the islands.
A black fronted tern flies over one of the islands.
A black fronted tern chick on one of the Waitaki islands in summer 2017.
A black fronted tern chick on one of the Waitaki islands in summer 2017.

Chris Eccleston.
Chris Eccleston.
New islands in the Waitaki River are part of the fight to stop the decline in numbers of the black fronted tern and black billed gull.

In October 2016, Environment Canterbury [Ecan] announced that close to $180,000 over five years had been allocated towards initiatives to protect habitats for the threatened species in the Lower Waitaki.

With the first year in the funding block coming to an end, Ecan Waitaki Zone manager Chris Eccleston said a lot had been achieved.

During winter 2016, Ecan river engineers created seven island sites totalling 6.6ha by removing weed vegetation from  islands and using a bulldozer to pile loose shingle up into new islands. The follow-up work was weed spraying in the spring.

"A number of threatened river bird species immediately took up residence on the new islands in spring. One island supported a large black-billed gull colony of more than 700 birds on nests, and two islands supported large black fronted tern colonies — 80 birds and 150 birds on nests.

"Wrybill were observed breeding on five of the islands and banded dotterel on six of the islands. Both of these braided river specialists are ranked as ‘vulnerable’."

The breeding success of 189 black-fronted terns was monitored on vegetated and cleared islands using remote cameras and walk-through checks, he said.

It had been found that the islands that had been created were virtually  predator free, compared to the mainland sites and fully vegetated islands.

"We are pleased to report that there was no predation of black-fronted terns by introduced mammalian predators on the new vegetation-free islands."

"These communities are subject to a number of threats, particularly predation by exotic mammals, weed invasion and human recreational activities on rivers. The result of these activities is that biodiversity values in braided rivers are in decline."

A Department of Conservation [DOC] fact sheet stated black fronted terns were nationally endangered and the conservation status of black billed gulls was nationally critical.

DOC and the University of Otago were also involved in the Waitaki work.

shannon.gillies@odt.co.nz

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